Time of flight methods are an established way to measure the distance in 3D space; especially on longer distances this technology is often called LIDAR (equiv. RADAR). Short pulses (1-10 ns) or sequences of pulses (pulse trains) of light are sent out and the time until reflected light returned is measured. Repetition rates are relatively low in order to limit total power but must be high enough to allow for scan/frame rates sufficient for a safety relevant function. In combination with a scanning mirror a very good angular resolution can be achieved. Pulse trains are used in order to simplify the identification of the detected laser light by comparing the pattern of the emitted pulse train with the pattern of the received pulse train. The required brightness can only be achieved by specialized solid-state or edge emitting lasers.